Polyaspartic acid has been formed by a number of methods.
Koskan et al., U.S. Pat. No. 5,116,513, teaches the formation of polyaspartic acid by the polymerization of aspartic acid powder. The polymerization produces a polysuccinimide, which can be base hydrolyzed to polyaspartic acid.
Boehmke et al., U.S. Pat. No. 4,839,461 teaches the production of polyaspartic acid by reacting maleic acid and ammonia in a molar ratio of 1:1 to 1.5 at 120.degree.-150.degree. C.